A Thin Film Transistor Liquid Crystal Display (TFT-LCD) is formed by arranging a Thin Film Transistor (TFT) array substrate and a Color Filter (CF) substrate oppositely to form a cell, with liquid crystals being filled between the TFT substrate and the CF substrate. To output different image, the liquid crystals are driven to rotate by controlling a variation of a voltage on the TFT substrate. In a cell-forming process, one of the most important steps is a cell alignment step, i.e., arranging the TFT substrate and the CF substrate oppositely to from a cell within a preset accuracy range in accordance with design requirements. Reference is made to FIG. 1, which is a schematic diagram of cell alignment of a TFT substrate 101 and a CF substrate 102. In the process of the cell alignment, the most important factor is an alignment mark 103 for the cell alignment. If the alignment mark 103 goes wrong, for example, a zigzag residue is formed at an edge of the alignment mark during rubbing of the TFT substrate due to the stacking of small residual particles on the TFT substrate, then the cell alignment cannot be achieved accurately, thereby resulting in various defects of the TFT-LCD, such as Mura defects and Zara defects.